Compressor intended to compress coolant fluid for a refrigeration or air conditioning installation

ABSTRACT

A compressor intended to compress coolant fluid for a refrigeration or air conditioning installation, comprising a substantially vertical body consisting of a casing intended to receive in particular a lubricating liquid in its bottom portion forming a reservoir, and means of heating the lubricating liquid. The means of heating the lubricating liquid and means of acoustic insulation and thermal insulation situated below the heating means are placed close to the bottom wall of the casing.

The present invention relates to a compressor intended to compress thecoolant fluid for a refrigeration or air conditioning installation.

BACKGROUND OF THE INVENTION

In a known manner, the phenomena of migration of the coolant fluidwithin a refrigeration or air conditioning circuit appear when thelatter is not in service.

Specifically, when the compressor is at a lower temperature than that ofthe heat exchangers, the coolant fluid migrates, under the temperaturegradient effect, from the heat exchangers to the compressor.

This phenomenon occurs particularly in the morning, when theinstallation is situated outdoors, the heat exchangers being heated bythe sun and rising in temperature more rapidly than the solid parts ofthe compressor which have a greater thermal inertia.

This phenomenon occurs in the reverse direction after the sun goes down,the coolant fluid migrating from the compressor to the heat exchangers,which cool down more quickly than the compressor.

During these migrations in the cooling circuit, the cooling fluid, bymoving in the different portions of the cooling circuit, may cause themechanical parts to be washed by condensation, carrying away the fluidlubricating the walls of these parts.

Furthermore, in the casing of the compressor toward which the coolantfluid migrates, the coolant fluid and the lubricant mix together, thesetwo fluids in liquid form being miscible, the mixture having the effectof reducing the viscosity of the lubricant.

Consequently, when the circuit is returned to service, the lubricationis insufficient, due to the washing of the mechanical parts and thereduction in viscosity of the lubricant, which may cause premature wearor even a breakage of the mechanical parts of the installation.

The known solutions for resolving this problem consist first in havingnon-return valves at the outlet of the compressor, on the dischargeside, and secondly in heating the compressor casing, and thus thelubricant contained in this casing.

This heating prevents the appearance of the temperature gradientdescribed hereinabove and hence the appearance of the migrationphenomenon.

The two solutions are ideally employed in parallel for greater security.

DESCRIPTION OF THE PRIOR ART

In existing compressors, as described in document U.S. Pat. No.5,252,036, the heating device is situated on the side wall of thecompressor. A seal surrounds the heating device in order to prevent anexcessive heat loss toward the outside.

However, this arrangement is not very advantageous because it cannot beused to heat all the oil by making use of the convection currents in thecasing to heat the lubricant uniformly. On the other hand, placement onthe side wall is disadvantageous because it allows major heat loss byforced convection due to the wind.

Document U.S. Pat. No. 4,208,883, which describes a device for thermallyregulating the temperature of the lubricant, suggests positioning theheating device beneath the compressor. In this document, the heatingmeans are regulated by a device making it possible to control thetemperature of the lubricant.

However, no measure is taken to reduce the heat loss through radiation.

In the known types of device, the criterion used to ensure that themigration does not occur is to maintain a temperature difference betweenthe lubricant contained in the casing and the outside temperature of theorder of 10 K by heating.

Consequently, powers of the order of 75 to 150 W are needed to power theheating devices. This power may have to be adjusted to suit the size ofthe compressor.

In addition to the migration phenomena, a second important technicalproblem relating to the compressors of the prior art concerns theiracoustic emissions.

To reduce the noise emitted by these compressors, a first solution usedin the prior art is to cover the compressor with an absorbent jacketwhich can be used to achieve an attenuation of the order of 7 dB,particularly effective for high frequencies, above 800 Hz.

However, the jackets are not effective in reducing the emitted lowfrequency noise, and they also constitute devices of complex structurecombining several materials whose cost is high compared with the cost ofthe compressor.

A second solution is described in document JP 53 099504, the compressorbody being mounted on springs in a compartment, this compartment itselfbeing mounted on springs passing through a layer of acousticallyinsulating material, in the form of solid or liquid foam situated in ahousing integral with the compressor attachment support.

This document consequently describes a complex device, in which thecompressor is completely contained in a compartment, this dispositionmaking access to the latter difficult and involving the installation ofan intermediate platform supporting the compartment, which increases theoverall space requirement of the compressor.

Other documents, such as document JP 2002 243211, also describe devicesin which a compartment completely contains the compressor, in order toreduce the emitted noise.

These devices also have disadvantages of space requirement and complexstructure and cost.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a compressor which, ina restricted space requirement and a simple construction, can be used toachieve heating requiring a reduced energy consumption, and to emit areduced acoustic power, particularly in the low frequencies.

Accordingly, the subject of the present invention is a compressorintended to compress coolant fluid for a refrigeration or airconditioning installation, comprising a substantially vertical bodyconsisting of a casing intended to receive in particular a lubricatingliquid in its bottom portion forming a reservoir, and means of heatingthe lubricating liquid, wherein the means of heating the lubricatingliquid and means of acoustic insulation and thermal insulation situatedbelow the heating means are placed close to the bottom wall of thecasing.

Such a disposition can be used to reduce significantly the powerconsumed to heat the lubricating liquid, because the heat insulationmeans reflect the energy toward the compressor and the dissipations dueto the wind are diminished.

This disposition can also be used to reduce to a surprising degree theemitted acoustic power, particularly in the field of the lowfrequencies, because it appears that the low frequency waves are emittedto a greater degree at the bottom wall of the casing.

This disposition is also used, with the abovementioned advantages, tocause a minimal space requirement.

Advantageously, the acoustic insulation and thermal insulation means areat a distance from the support to which the compressor is attached.

According to one embodiment, the acoustic insulation and thermalinsulation means comprise at least one layer of insulating material.

Advantageously, at least one layer of insulating material comprises acellular material.

According to one embodiment, at least one layer of insulating materialcomprises felt.

Advantageously, at least one layer of insulating material comprises afibrous material.

Advantageously, the acoustic insulation and thermal insulation meansalso comprise a rigid support plate.

According to one embodiment, the acoustic insulation and thermalinsulation means also comprise a film for protecting and retaining theinsulating material.

Advantageously, the thermal and acoustic insulation means have a topsurface whose shape at least in part substantially complements that ofthe bottom wall of the casing.

According to one embodiment, the heating means comprise at least oneelectric resistance attached to the bottom wall of the casing, outsidethe latter.

Advantageously, at least one electric resistance is attached to thebottom wall of the casing by adhesive means.

According to one embodiment, the thermal insulation and acousticinsulation means are kept in position relative to the compressor body byattachment means.

Advantageously, the attachment means comprise at least one elastic clipkept in position by gripping a projecting portion of the compressor anda substantially horizontal lug, the thermal and acoustic insulationmeans pressing on the lugs of the attachment means.

According to one embodiment, the attachment means are at least two innumber.

Advantageously, the thermal and acoustic insulation means allow theattachment feet of the compressor to pass through.

According to one embodiment, the compressor comprises an acousticinsulation jacket covering the body of the compressor.

The present invention also relates to a thermodynamic machine using atleast one compressor as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

In any case, the invention will be clearly understood with the aid ofthe following description, with reference to the appended schematicdrawing, representing, as a nonlimiting example, an embodiment of acompressor according to the invention.

FIG. 1 is a general view in perspective.

FIG. 2 is a view in section on a larger scale along II-II of FIG. 1.

FIG. 3 represents a partial exploded view in perspective of thecompressor of FIG. 1.

FIG. 4 represents schematically an acoustic emission spectrum of acompressor according to the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A compressor 2 intended to compress coolant fluid for a refrigeration orair conditioning installation according to the invention is representedin FIGS. 1 to 3. This compressor comprises a substantially vertical body3 comprising a casing 4 intended to receive in particular a lubricatingliquid 5 in its bottom portion forming a reservoir.

In this embodiment, the compressor casing comprises a side wall 11 and abase plate 6 having a dish-shaped central portion 7, intended to formthe bottom wall of the casing, bordered by a peripheral rim 8, alsocomprising attachment orifices 9 for first means of attachment 10 to asupport 12, situated outside the peripheral rim 8, and a return 13 madeon the edge of the plate 6 and directed downward.

The side wall 11 and the base plate 6 are attached at the rim 8, thelower edge of the side wall 11 resting on the outside of the rim 8forming an abutment.

The first attachment means 10 consist, in a known manner, of a stud madeof elastic material 14 of the rubber type forming a supporting foot forthe compressor and having a longitudinal opening in which can be houseda bolt 15 intended to be housed also in an opening 16 of the support 12.

According to an essential feature of the invention, the compressor 2comprises means 17 of heating the lubricating liquid 5, placed close tothe bottom wall 7 of the casing, and acoustic insulation and thermalinsulation means 18 placed beneath the heating means 17.

The heating means consist of an electric resistance 17 attached to thebottom wall 7 of the casing, outside the latter, attached to the bottomwall of the casing by adhesive means 19, and intended to be connected toan external source of electric power by two connecting conductor wires20.

The acoustic insulation and thermal insulation means 18 consist of amember having a top surface whose shape substantially complements thatof the bottom wall of the casing 7, comprising the following elements,superposed from the bottom up:

-   -   a flat rigid support plate 22,    -   a layer of cellular insulating material 23, whose shape        substantially complements that of the bottom wall 7 of the        casing,    -   a film 24 made of plastic material, protecting and keeping the        cellular material in position, the film being bonded or heat        sealed to the flat plate 22 on the periphery of the latter.

According to a variant, the layer of insulating material comprises felt.

According to another variant, the layer of insulating material comprisesa fibrous material, such as glass fiber or rock wool.

The thermal insulation and acoustic insulation means 18 are held inposition relative to the compressor body by second attachment means 25each comprising an elastic clip 26 held in position by gripping thereturn 13 of the compressor base plate 6 and a substantially horizontallug 27, the flat and rigid plate 22 supporting the thermal and acousticinsulation means resting on the lugs 27 of the second attachment means25.

These second attachment means 25 are four in number and preferably atleast two in number depending on the variants.

These second attachment means are used to make it easier to install andremove the thermal and acoustic insulation means 18 on/from thecompressor body 2.

The thin insulation means 18 are thus held in position beneath thecompressor, without contact with the support 12, and delimit a housingfor the heating means with the thin bottom wall of the casing.

This disposition is particularly helpful in protecting the heating means17 from the effects of the wind, which cannot cause a major heat loss.In addition, the heating means are placed beneath the casing, thusmaking it possible to cause in the latter a uniform temperature mix ofthe lubricating liquid by convection currents.

Furthermore, the thermal and acoustic insulation means 18 are separatedfrom the support, which assists with this insulation.

It is therefore possible to maintain a temperature with an electricpower of the order of 50 to 60 W, hence much less than that of thedevices of the prior art, thus allowing a smaller dimensioning of theheating means power supply circuit.

The thermal and acoustic insulation means 18 have a horizontal crosssection allowing the compressor attachment feet 14 to pass through.

In a known manner, the acoustic emission spectrum of a compressoraccording to the prior art has a curve as shown in FIG. 4, the power Pbeing represented on the y axis and the frequency F on the x axis.

It appears on this curve that the compressor has a considerable emittedpower in a frequency band situated around 600 Hz.

The dispositions according to the invention make it possible to obtain areduction in the emitted power in this band, the attenuation being ofthe order of −5 dBa.

This result is important, because the insulation jackets covering thewhole compressor body do not make it possible to obtain a significantattenuation in this frequency band.

According to a variant, the compressor also comprises an acousticinsulation jacket 28 shown in dot-and-dash lines covering the compressorbody 2.

The addition of this jacket makes it possible to obtain an attenuationof the order of −7 dBa, in a frequency band situated above 900 Hz.

The addition of this jacket on the compressor according to the inventionmakes it possible to obtain an overall attenuation of the order of −14dBa across the whole spectrum.

This unexpected result is obtained thanks to the action of theinsulation means on one frequency band, and to the action of the jacketon a different frequency band.

As it goes without saying, the invention is not restricted to thepreferred embodiment described hereinabove, as a nonlimiting example; onthe contrary it embraces all the variant embodiments thereof in thecontext of the following claims.

Thus, it is possible to use several different layers of insulatingmaterials.

Also, the measurements taken for one embodiment of the invention arecited as an example; these measurements may be different for otherembodiments.

1. A compressor for compressing coolant fluid for an air conditioninginstallation, comprising a substantially vertical body comprising acasing for receiving a lubricating liquid in its bottom portion forminga reservoir, and means of heating the lubricating liquid, wherein themeans of heating the lubricating liquid and means of acoustic insulationand thermal insulation situated below the heating means are placed closeto the bottom wall of the casing.
 2. The compressor as claimed in claim1, wherein the acoustic insulation and thermal insulation means are at adistance from the support to which the compressor is attached.
 3. Thecompressor as claimed in claim 1, wherein the acoustic insulation andthermal insulation means comprise at least one layer of insulatingmaterial.
 4. The compressor as claimed in claim 3, wherein at least onelayer of insulating material comprises a cellular material.
 5. Thecompressor as claimed in claim 3, wherein at least one layer ofinsulating material comprises felt.
 6. The compressor as claimed inclaim 3, wherein at least one layer of insulating material comprises afibrous material.
 7. The compressor as claimed in claim 3, wherein theacoustic insulation and thermal insulation means also comprise a rigidsupport plate.
 8. The compressor as claimed in claim 3, wherein theacoustic insulation and thermal insulation means also comprise a filmfor protecting and retaining the insulating material.
 9. The compressoras claimed in claim 1, wherein the thermal and acoustic insulation meanshave a top surface whose shape at least in part substantiallycomplements that of the bottom wall of the casing.
 10. The compressor asclaimed in claim 1, wherein the heating means comprise at least oneelectric resistance attached to the bottom wall of the casing, outsidethe latter.
 11. The compressor as claimed in claim 10, wherein at leastone electric resistance is attached to the bottom wall of the casing byadhesive means.
 12. The compressor as claimed in claim 1, wherein thethermal insulation and acoustic insulation means are kept in positionrelative to the body of the compressor by attachment means.
 13. Thecompressor as claimed in claim 12, wherein the attachment means compriseat least one elastic clip kept in position by clipping a protrudingportion of the compressor and a substantially horizontal lug, thethermal and acoustic insulation means pressing on the lugs of theattachment means.
 14. The compressor as claimed in claim 13, wherein theattachment means are at least two in number.
 15. The compressor asclaimed in claim 1, wherein the thermal and acoustic insulation meansallow the attachment feet of the compressor to pass through.
 16. Thecompressor as claimed in claim 1, which comprises an acoustic insulationjacket covering the body of the compressor.
 17. A thermodynamic machineincluding at least one compressor as claimed in claim 1.